How can I play a crazy character?

Solution 1:

The Lunatic and Possessed traits are given by events. In the base game, these events can happen randomly. There are other ways to gain the traits or to make these events more likely but, as far as I can recall, all are in DLCs.

The easiest way to add these traits, without ruler designer, is to cheat and use the console. To do this, you need to be in a non-ironman game. Press the ` key (it's the one to the left of the 1 key) to open the console.

The code to trigger events is

event (eventID)

The specific events you want are:

Lunatic:

event 6020

Possessed:

event 6030

Here's a list of console commands if you want to add other traits. Or remove them, if you get sick of employing horses as chancellors.

Solution 2:

If you own Way of Life DLC, then you can pick learning focus, obtain Necronomicon, and after that there is an option that gives you lunatic trait with 10-15% chance.

Another way is to have a character with a combination of negative traits: paranoid, depressed, zealous, have a fever or being imprisoned - in other words - have conditions that may drive a man to maddness in real life. Than you have to wait.

If you are not afraid to dig into config files of the game, you can search various event files (located in the 'events' folder of the game) for this event:

# Become Lunatic
character_event = {
    id = 6020

and trace further all the required conditions. You goal is the outcomes with the line

add_trait = lunatic

and

add_trait = possessed